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Jul 23, 2017, 11:52 AM
Patrick Randall
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4 servo wing - 90 deg flaps on landing alongside ailerons?

I'm about to set up an old 6 servo Stratos LE (3m electric glider) with a new radio (Taranis X9D+) - I used to fly this on a Futaba 8Ua and had "glide slope" flap control on the bottom half of the throttle stick with motor going from 0-100% on the top half. I am sad to say that I can't remember how I had it working (was 10 years ago) - the Futaba had an inbuilt setup for full house sailplanes where it mixed a little flaps with the ailerons for regular flight. I think I then flicked a switch to go to "landing mode" and that *might* have disabled the aileron to flap mix above and *might* have activated the throttle stick 49%-0% control of the flaps going from 0 to 90 degrees.
All I can say it was nice to be able to have instant go-around on the throttle stick.
Now my question is this - is that the way to do things? Should the aileron-flap mixing be disabled for approaches leaving just ailerons for roll control?
I'd appreciate any experienced chaps' guidance!
SW Florida
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Jul 23, 2017, 08:36 PM
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I just saw one of those at an ALES contest last weekend.

I think a lot of people put the motor on a switch now, though I've also heard of some kind of mode switch so the throttle stick can also be used for flaps.

My sailplanes with 5 or more servos are set up with CROW. That is, move the flap stick past a certain point and the ailerons go up instead of down. When doing this, it's useful to have reverse aileron differential added in as the ailerons get up higher. Fancy Airtronics radios used to do this. Some won't respond well to the ailerons in CROW without this mixing. If you keep the same flap to aileron mix for large deflections of the flaps, you might as well use rudder only for roll control. This is noticeable in DLG's.

I only have a little experience with complicated sailplanes used in ALES, but I have quite a bit with them minus a motor. Using a switch was fine for my 3 meter ALES model. (RIP)
Jul 23, 2017, 10:22 PM
Going in circles.
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I also have a little bit of flap mixed with my ailerons (about 33% is pretty typical). Since I don't currently use a landing mode the mix is always on, even with flaps fully deployed. I haven't noticed any odd behaviors from it, but if I were using a landing mode I'd be inclined to have the mix turn off when landing. I don't think the flaps are contributing to your roll control when they're deployed enough for braking, so I can't see the benefit of having the coupling turned on during landing. Maybe with the Taranis you can have the mix turn off automatically for larger flap deflections?
Oct 26, 2020, 10:24 PM
cityevader's Avatar
I use a 3-way switch.
1) Flaps only
2) Crow
3) Spoilerons
Why? I fly slope soarers mostly and different sites have different lift characteristics across the LZ requiring different braking techniques.

And yes, when using flaps only, I separate the ailerons.
With any mode, there can be lots of pedaling of the "throttle" stick, so for me, having throttle on a switch is vital.
Oct 27, 2020, 09:33 AM
Barney Fife, Vigilante
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I leave my aileron - flap mixing enabled through the landing mode. One thing to play with if your radio is capable is to max out your differential in the landing mode so that the "down" control surfaces don't move down with aileron input, but the "up" side moves significantly up. Roll control is already significantly muted in the landing phase because of lowered airspeed and reduced AoA of the outer wing. You don't want to reduce it further if you can avoid. Only moving surfaces up with aileron input also ensures that you don't force a tip stall by correcting roll. All rolling input in this situation reduces AoA across the span, keeping you flying through the approach.

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